a) Field of the Invention
The present invention relates to the use of a lightweight mineral foam like the one disclosed and claimed in U.S. Pat. No. 5,360,771 issued on Nov. 1st, 1994 with designation of the present inventors, for the manufacture of a decorative, non-combustible synthetic fire-log.
The invention also relates to the synthetic fire-log that is so-obtained and to the use of such a synthetic fire-log as a substitute for a natural wood-log in a gas-or oil-burning fireplace or stove.
b) Brief Description of the Prior Art
Synthetic fire-logs for use in fireplaces or stoves are well known products.
U.S. Pat. No. 678,346 issued in 1901 to C. W. METTLER and U.S. Pat. No. 734,743 issued in 1903 to A. PAUL both disclose synthetic fire-logs made by compression of sawdust and coal dust with a liquid binder.
U.S. Pat. No. 764,526 issued in 1904 to M. C. GAMA also discloses a synthetic fire-log made by compression of sawdust and coaldust with crude oil, residues of refined oil and tallow.
U.S. Pat. No. 4,179,269 issued in 1979 to W. L. YATES discloses a synthetic fire-log made by extrusion of a mixture of coal, wood chips and molten slack wax at a temperature of 80 to 95AF.
U.S. Pat. No. 4,333,738 issued in 1982 to J. SCHRADER discloses synthetic fire-logs made by compression of sawdust or wood chips with coal liquid, molasses and paraffin wax in appropriate quantities.
All the synthetic fire-logs disclosed in the above patents are combustible and intended to be used either in combination with or as a substitute for natural wood-logs in a conventional, wood-burning fireplace or stove.
More recently, non-combustible synthetic fire-logs have also been devised, for use as a decorative substitute for natural wood-logs in an oil-or gas-burning fireplace or stove. In this kind of burning equipment, wood is not required as a combustible and must even be avoided. However, it is often required that such an oil-or gas-burning fireplace or stove looks like its wood-burning homolog, thereby making it necessary to use "fake logs".
An example of such a non-combustible, decorative fire-log intended to be used in combination with combustible synthetic fire-logs is disclosed in U.S. Pat. No. 5, 118,539 issued on Jun. 2nd, 1992 to D. SEBBY et al. Usually, such non-combustible fire-logs are made of cement and refractory aggregates or ceramic fibers, and have a density as high as 120 to 160 lbs/ft.sup.3.
U.S. Pat. No. 5,271,888 issued on Dec. 21, 1993 to W. SINSLEY discloses "an improved process and partible mold for forming a lightweight synthetic ceramic log for use in natural gas, propane and wood-burning fireplaces and stoves which are both fully-vented and non-vented depending upon the particular design of the heat generating equipment".
In this process, the log is produced by vacuum forming using, as starting material, a mixture of aluminosilicate fibers (viz.ceramic fibers) and chromite dispersed into water, to which is added a flocculating composition including starch possessing a negative charge to facilitate solid formation, and a colloidal silica/sol possessing a positive charge to improve the adherence of the fibers to each other and thus to improve the handling properties of the resulting molded log. Thanks to the chromite component and to other mineral pigments that can be added to the composition, the log that is so-produced has a bark-like exterior surface and a dark color that make it particularly useful to simulate a natural looking arrangement of real wood-logs in an aesthetically-appealing oil-or gas-burning environment.
A major problem with all the existing non-combustible, synthetic fire-logs known to the present inventors is that they are made of, or include ceramic fibers, the use of which is more and more subject to stringent environmental regulations because of the dust that is generated by these fibers in the ambient atmosphere.
Another problem with some of the non-combustible synthetic fire-logs known in the art is that their density is very high (more than 100 lbs/ft.sup.3), thereby making the resulting logs very heavy and difficult to handle in bulk.
A further problem with some other non-combustible, synthetic fire-logs known in the art, is that they generate soot and do not have the same glowing aspect in use as the corresponding natural wood-logs.
Still another problem with most of the existing, non-combustible, synthetic fire-logs known in the art is that they infer with the flame coming from the gas or oil burner and prevent completion of the combustion, thereby resulting in the release of dangerous, unwanted carbon monoxide in the ambient atmosphere.